Ergo, "mommy's basement."
The reason I love this counter-punch is because not only is it common, and not only is it part of a prepackaged suite of knee-jerkism ("can't get laid" "small penis" etc.) it's because it belies that the person accusing you of living in mommy's basement has lost the argument.
You've won, that person lost, and the reasons are multi-fold.
One, do you REALLY live in mommy's basement?
Of all the bloggers, commenters, podcasters, etc., I know none of them live in their "mommy's basement" let alone receive a STIPEND or subsidy from their parents or government like most "mommy's basement accusers" do. Are there basement dwelling trolls who make trolling comments?
But what should concern most people who resort to this argument is the fact that there are so many self-supporting men who are merely voicing their legitimate opinion. And accusing them of "living in mommy's basement" is...well...pat-on-the-head-worthy "cute." It's not true, so the accusation rings hallow, and an eye roll ensues.
Second, the "mommy's basement" is a CLASSIC liberal debating technique of changing the topic. If the current debate or discussion at hand is untenable a hypocrite will ALWAYS go personal because they know deep down inside they're wrong and their adversary is right. The real issue is whether you have the self-control not to fall for this ruse, take personal affront, and then go on defending how you "don't live in your mommy's basement." Maintain control of the debate, ignore these personal sleights, and continue your assault.
Finally, I'm not a big "psychology" guy and don't really believe in this "projection" kind of thing younger generations resort to as a means to debate. But I am a big believer in "deflection." Realize when somebody is so desperate, so hypocritical, and above all else, exposed for their self-serving and immoral beliefs, their little lizard-brain goes into full defense mode and tries to cover up their true intention of basically stealing resources from other people. However, since they have no legitimate moral or logical argument, they need to resort to name calling. As previously mentioned, this is merely a ruse and proof you've won the debate, but I wanted to point out just how cowardly, pathetic, and "loserish" it is of the person that has to resort to this tactic.
In the end, the true "loser" is not the guy (or gal) accused of living in "mommy's basement." It's the person doing the accusing. They're typically a spoiled suburbanite brat that had everything handed to her (or him), never had to support themselves, and never had enough adversity in life to challenge them and forge them into a real, interesting, and self-supporting adult. And so when reality smashes their fragile idealistic view of the world in the form of a genuinely independent person, speaking real truths, their tantrums, and any accusations of living with mommy, can largely be dismissed.